One thing is statistically certain with that number of custodians: the legal hold will not be followed to perfection. If I were more mathematically inclined I’d say it could be reduced to a formula along these lines:
Legal hold compliance *decreases* exponentially as you multiply:
* The number of custodians
* The length of time the legal hold is in effect
* The types and volumes of potential ESI that may be relevant
* The presence of individuals who don’t want data to be preserved due to their own perceived errors/foibles/omissions
The answer, in my mind, doesn’t lie in a better mouse trap to manage the vagaries of the legal hold process. No, the best way to take the risk out of the legal hold process is to move very rapidly from preservation to collection.
This is going to be closely litigated as more and more security contractors are dragged into court, one way or another.